Corrugated wood sheets and articles having a multi-ply panel wall structure comprising same

ABSTRACT

Receptacles having a multi-ply panel wall structure. The multi-ply panel comprises primarily natural and/or bio-degradable fibrous or cellulose materials, such as wood. The wood multi-ply panel is processed and formed by pressing multiple layers of thin wood sheets that retain their natural grain structure. The sheets are heat pressed molded to shape into the desired receptacle configuration, which may be done in a single step. The wood layer may have a corrugated sheet structure.

FIELD OF THE INVENTION

The present invention relates to wood panels and articles comprising same.

BACKGROUND OF THE INVENTION

Disposable receptacles are commonly used to serve or package food, for example at fast food restaurants. Heretofore, disposable receptacles are primarily structured using plastic and paper. These types of receptacles create significant concerns to the world we live in.

Plastics for receptacles are developed from byproducts of natural oil reserves. As such, they deplete valuable natural resources, which should be conserved. Plastic containers may be formed to the receptacle configuration in a single step from an intermediate, for example by molding. Given that the chemical structure of plastics is relatively unstable, heat applied during the molding process may release chemical substances. For plastic containers designed for serving or packaging food, the form plastic material could release harmful substances that are absorbed by the food. Consumption of such tainted food would be seriously harmful to human health and safety. Disposal of plastic containers creates serious pollution concerns to our environment. Plastics are relatively difficult to bio-degrade in nature. For example, it has been a long felt concern that white plastic form receptacles over-used by the fast food industry, creating a serious case of what has been referred to as “white pollution”.

Paper receptacles are made from natural fibrous or cellulose pulp material, such as wood pulp, reed pulp, or intermediate material such as paper stock, etc. Some paper receptacles may be shaped from the material in a single step, e.g., by molding wood pulp. Disposal of paper receptacles create less pollution concerns, as pulp materials are relatively easier to bio-degrade in nature. However, the processes of making paper products consume significant amount of water resources, and create harmful chemical byproducts. Pulp and paper productions consist generally a series of processes: pulp production, pulp processing and chemical recovery, pulp bleaching, stock preparation, and paper manufacturing. Some of these processes require use of chemicals such as bleaching agent, softeners, conditioners, dyes, detergents, etc. These chemicals alone, or after reacting with raw materials, produce industrial waste that seriously pollutes our water resources, creating a serious case of what has been referred to as “black pollution”.

In addition to pollution concerns, the manufacturing processes for paper receptacles are relatively more complicated and costly. The structural integrity of paper receptacles is relatively weak, which does not serve well in certain applications.

Besides plastic and paper receptacles, wood receptacles have been developed for limited use. The cellular structure of wood and the physical organization of the cellulose chain within the cell wall make the physical and mechanical properties of wood dependent upon the direction of loading. Wood may be described as an orthotropic or anisotropic material; that is, it has unique and independent mechanical properties in the directions of three mutually perpendicular axes, with the longitudinal axis generally parallel to the long axis of the wood fibers (i.e., generally in the direction of the grain), the tangential axis and radial axis (i.e., in relation to cylindrical trunk of the tree) generally perpendicular to the grain. The mechanical properties of wood parallel to the grain are higher than that perpendicular to the grain, since the grain direction is also the direction of the primary bonds of the major chemical constituents of the wood cell structure. Because of this anisotropic behavior, thin walled wood structure is typically weak to withstand bending load, and may crack easily. To increase the structural integrity, the size and thickness of the wood structure must be increased. Heretofore, wooden receptacles have a relatively heavy and bulky structure that is carved from a solid block of wood or assembled using wood panels. The receptacle configuration therefore cannot be formed by a single step from a starting or intermediate material. Processing of natural wood lead to significant wastage of wood material (e.g., in wood pieces, shavings and dust). The final product may only retain one third of the starting raw material. Also wood processing requires more steps, thus increasing production costs. Further, untreated wood may transport pests and germs that may harm the environment. These deficiencies lead to low utility of wood receptacles and acceptance by the packaging industry, especially for the food packaging industry.

It is therefore desirable to develop receptacles that have good structural integrity, are relatively simple and cheap to manufacture, and are yet environmentally friendly.

SUMMARY OF THE INVENTION

The present invention is directed to wood panels and articles having a multi-ply panel wall structure. The wood panel comprises primarily, and preferably, natural and/or bio-degradable fibrous or cellulose materials, such as wood. The multi-ply panel may comprise primarily the same material for its structure, or a combination or composite of different types of materials.

According to one aspect of the present invention, wood multi-ply panel is processed and formed from multiple layers of thin wood sheets that retain their natural wood grain, fiber or cellulose structure. The sheets may be pressed formed (e.g., using a mold with application of heat and pressure) into the desired configuration of the article in a single step. The multi-ply panel structure provides improved structural integrity in a light-weight structure. The multi-ply panel structure may be in the form of a laminated structure.

In one embodiment, the wood used for processing and forming the wood multi-ply panel is selected from trees that are of the type that matures in relative short period of time, such as between 5 to 15 years. The sheets of wood are sliced generally along or with the grain of the wood. In one embodiment, the sheets of wood are sliced from a tree trunk in a circumferential spiral fashion.

The sheets may be stacked with the grains of adjacent layers arranged in generally orthogonal directions, or generally parallel or in the same directions, or generally diagonally at an angle therebetween with respect to each other, depending on the structural properties desired. The orthogonal arrangement would provide a more rigid and/or stronger structure, and the unidirectional arrangement would provide a more flexible structure at least for bending along the grain. The sheets are compressed in a mold to shape into the desired configuration of the article having a multi-ply panel wall structure, which may involve a single molding step or multiple molding steps. The sheets may be pre-formed into a multi-ply panel or laminated panel, which is then used to mold into the desired shape of the article.

In another embodiment of the present invention, the layering of thin wood layers may be strategically designed to provide different structural properties at different sections of the article. The article does not need to have uniform layers across the structure. Some sections may have more layers than other sections, and some sections may have orthogonal layers (e.g., at the edges of the article) and other sections may have unidirectional layers, to provide the desired specific structural characteristics (e.g., rigidity, flexibility) at specific sections and the overall structural characteristics for the particular article configuration. The sheets may be arranged or distributed in a roof tile fashion, with terraced or feathered layers, such as to form a gradually thinning edge upon heat pressing.

One or more layers of the multi-ply panel may be formed from an initial corrugated sheet structure (resembling roof tiles having a wavy cross section, with alternating ridges and grooves), to facilitate shaping of the multi-ply panel into the receptacle configuration (e.g., improving flexibility and moldability of the panel in a molding process). The corrugated sheet may have natural wood grains generally parallel or orthogonal to the corrugations. Alternatively, the corrugated sheets are stacked to preform a corrugated panel, which are used as is or subsequently applied to a molding process to form the desired receptacle structure. The corrugated panel may have a hollow structure defined by the corrugated sheet and an adjacent sheet. Different panels having different corrugated structure and/or profile, layers and structural characteristics may be preformed. These preformed panels may be selectively applied to configure the base material structure for press forming the article configuration. Appropriate glue may be applied to the sheets of wood to fix the relative position of the sheets to form the generally planar panel structure. The corrugated panel structure is then subject to heat pressing to form the desired article structure.

The pressed structure may be trimmed to provide a more desirable finish on the edges, or additional features may be formed or provided to the pressed structure (e.g., holes are drilled or other components are attached). Intermediate or finish layers of synthetic or non-synthetic materials may be included in the multi-ply structure, to provide the desired physical properties and/or finish.

In a further embodiment of the present invention, a smooth or textured surface layer may be provided on one side or both sides of the multi-ply panel, to provide the desired texture and surface finish.

In a further aspect of the present invention, the articles are structured and configured as receptacles or packaging for serving or packaging food, for example for the fast food industry.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings. In the following drawings, like reference numerals designate like or similar parts throughout the drawings.

FIG. 1 is a schematic perspective view of a stack of thin wood sheets in accordance with one embodiment of the present invention.

FIGS. 2A-2D illustrate the process of molding the multi-ply panel into a receptacle in connection with one embodiment of the present invention.

FIG. 3A illustrate a corrugated wood sheet in accordance with one embodiment of the present invention; FIG. 3B is a sectional view taken along 3B-3B in FIG. 3A; FIGS. 3C-E are sectional views illustrating corrugated structure of other profiles.

FIG. 4 illustrates a stack of corrugated wood sheets with cross grain orientation in accordance with one embodiment of the present invention.

FIG. 5 illustrate the stacking of a combination of flat and corrugated wood sheets in various grain orientations in accordance with one embodiment of the present invention.

FIGS. 6 to 8 illustrate various embodiments of stacking wood sheets.

FIG. 9A illustrates a container in accordance with another embodiment of the present invention; FIG. 9B is a sectional view taken along line 9B-9B in FIG. 9A; FIG. 9C is a sectional view taken along line 9C-9C in FIG. 9A; and FIG. 9D is a sectional view taken along line 9D-9D in FIG. 9A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present description is of the best presently contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.

The present invention is directed to wood panels and articles having a multi-ply wood panel wall structure. The multi-ply panel structure may comprise primarily, and preferably, natural and/or bio-degradable fibrous or cellulose materials, such as wood. The multi-ply panel may comprise primarily the same material for its structure, or a combination or composite of different types of materials. For purposes of illustrating the present invention and not by limitation, the present invention is described hereinbelow in reference to wood as the primary material for the multi-ply panel, and in reference to receptacles. Other types of natural or biodegradable cellulose or fibrous materials may be used without departing from the scope and spirit of the present invention. As used herein, receptacles include all types of containers, vessels, holders, utensils, packaging, of all shapes and sizes, for retaining a fluid, solid, food or non-food items.

According to one aspect of the present invention, wood multi-ply panel is processed and formed from a stack 10 of multiple layers of thin flat wood sheets 12 that retain their natural grain structure, where arrows in FIG. 1 schematically represent the grain direction. The sheets may be stacked with the grains of adjacent layers arranged in generally orthogonal directions (as schematically represented in FIG. 1), or generally parallel or in or along the same directions (not shown), depending on the structural properties desired. The orthogonal arrangement would result in a more rigid and/or stronger structure, and the unidirectional arrangement would result in a more flexible structure at least for bending along the grain. While FIG. 1 illustrates a stack 10 of three sheets 12, more or less layers may be implement without departing from the scope and spirit of the present invention. With a stack 10, there may be two or more adjacent sheets 12 with grains arranged in the same direction, as well as two or more adjacent sheets 12 with grains arranged in orthogonal directions. The particular number of sheets 12 and the relative grain directions can be selected to obtain the desired mechanical strength, structural properties, and thickness of the finished multi-ply panel structure in the finished product (as described below, the stack 10 is subject to pressing and/or molding processes, for example, to shape the receptacle configuration.) Generally, adjacent sheets 12 having sheets 12 grains in parallel directions would render a structure that is more flexible to shape a bend along the grains, and sheets 12 having grains in orthogonal directions would render a structure that is less flexible to shape a bend. A combination of parallel and orthogonal structures may be selected to provide the desired flexibility, to render a structure that can be bent by as much as 90°.

One or more intermediate layers may be provided between the wood sheets 12 in the stack 10. For example, paper sheet, mesh sheet, gauze sheet, perforated sheet, felt sheet, knitted or non-knitted fabric, glue layer, and sheets of other synthetic or natural material, which may or may not be biodegradable, food grade and/or environmentally friendly. For particular applications in which certain structural characteristics are desired, an intermediate thin layer of metal such as aluminum foil may be used.

In one embodiment, the various layers are cut to size and stacked, before being compressed in a mold to form the multi-ply panel while shaping the desired receptacle configuration in a single step. The particular surface features of the mold, such as curvature, depth and angle of the surface features, and the spacing between complementary molding tools should be chosen to match the characteristics of the molded multi-ply panel to obtain the desired molded structure. In an alternate embodiment, as will be further explained below by further examples, the stack of sheets may be processed initially into a panel, to be used for shaping a receptacle in a separate process step.

The sheets 12 are pressed formed (e.g., using a mold with application of heat and pressure) into a desired receptacle configuration in a single step. The multi-ply panel structure provides improved structural integrity of the receptacle that has a light-weight structure. The multi-ply panel may be characterized as a laminated structure, comprising several lamination layers.

Referring to the embodiment illustrated in FIGS. 2A to 2D, the stack 10 of wood sheets 12 are molded into a receptacle 20, for example, by using a molding press.

FIG. 2A schematically shows a molding press, which is well known in the art. The molding press comprises two complementary molding blocks 14 and 16 made of metal, such as carbon steel, preferably with polished surface finish or the desired textured surface finish. Each molding block 14 and 16 is shaped with a profile necessary to shape the receptacle 20. The upper molding block 16 may be interchanged with the lower molding block. The stack 10 is placed in between the upper and lower molding blocks 14 and 16. The stack 10 should be provided with a planar area that would be sufficient for shaping the receptacle 20. Further, the planar area of the stack 10 is pre-shaped to complement the molding process, taking into consideration of the “flow” of material during the press molding process, so as to result in the desired configuration of the receptacle 20 with coverage of the pressed panel over the entire body of the receptacle 20, and without too much trimming required if possible. For example, the stack 10 a may be shaped as a generally rectangular area with slightly rounded corner. Alternatively, the stack 10 b may be shaped as a generally rectangular area with cutouts at the four corners. Pressure is applied to press the molding blocks 14 and 16 together to compress and shape the stack 10 to conform to the shape of the molding blocks 14 and 16, as shown in FIG. 2B. One or both of the molding blocks 14 and 16 may be heated. As the stack 10 is pressed, some sections of the stack 10 may be forced to overlap, or fold, or stretch, slightly in order to conform to the profiles of the molding blocks 14 and 16. In the case of stack 10 a, the rounded corner section may be folded or overlapped, and/or the center section may be stretched. In the case of stack 10 b, the cutouts at the corners facilitate overlapping of the sections adjacent the cutouts during press molding.

While it is not necessary to presoak the stack 10 prior to pressing and molding, such may be undertaken to prepare the stack 10 for molding. Depending on the particular molding process designed to work with the particular multi-ply wood structure, it is contemplated that oil, liquid or other material may be applied to the molds to facilitate release the molded receptacle, and ports may be provided on the molds to release steam or heated moisture to the stack.

In one embodiment, the wood sheets in stack 10 could be pre-moistened, which facilitates bending and stretching of the wood sheets with the heated molding blocks 14 and/or 16, without reduced tearing of the wood sheets. Alternatively, the molding block 14 and/or block 16 may be provided with ports to release steam on the stack 10 during the pressing process.

As shown in FIG. 2C, pressure is released to separate the molding blocks 14 and 16, and the receptacle 20 is released from the molding press. There may be excess material that may be required to be trimmed off to finish the receptacle 20 as shown in FIG. 2D. The receptacle 20 has a body 22 with a multi-ply panel wall structure. Further finish tasks, such as painting, may be undertaken if desired.

As is shown in FIG. 2A to 2D, the press molding process shapes the receptacle 20 in a single pressing step. For more receptacle having more complicated and/or large shapes, and/or more intricate structural details (e.g., more bends and/or surface features), more than one pressing step may be required, without departing from the scope and spirit of the present invention. For example, the stack 10 may be subject to a series of molding presses, each provided with molding blocks that shape the stack 10 in a particular sequence to obtain the final configuration of the receptacle.

Further, it is well within the scope and spirit of the present invention to provide pre-molding treatment steps prior to the molding process, or post-molding treatment steps after the molding steps, to further provide the desired structure for the receptacle. For example, prior to molding, the stack 10 may be pre-treated with a dye, bleach, or other effects as desired. The stack 10 may be provided with a plastic lamination top layer or other veneer, to allow for a smooth and/or waterproof finish, for example. Alternatively or in addition, after the molding process, the receptacle 20 may be dyed, colored, sprayed with a lamination material (e.g., a waterproof material), etc., to further provide the receptacle with the desired surface finish. The receptacle 20 may be further crafted or cut at desired locations to provide, for example, holes, hinges, etc., and/or other components, e.g., a hanger, clip, label, etc., may be attached. Further, two or more molded pieces may be coupled together (e.g., by gluing, stapling or stitching) to form a receptacle, or two or more parts of a receptacle of appropriate shapes may be coupled together (e.g., a cover and a base), with or without additional press molding steps.

To further facilitate shaping of the wood sheets in the stack during the press molding process, one or more wood sheets in the stack 10 may be initially provided with a corrugated structure. FIG. 3A is a perspective view of a corrugated wood sheet 24, and 3B is a cross-sectional view across the corrugations. The general direction of the grains of the corrugate wood sheet 22 is schematically show by the arrow in FIG. 3A (hereinafter referred to as in the direction of the corrugations or alternatively in the longitudinal direction of the corrugated structure (i.e., along the directions of the ridges 25 and grooves 26), as opposed to a direction across the corrugations or corrugated structure). The corrugated wood sheet 24 has a cross-sectional profile that resembles that of roof tiles having a wavy cross section, with alternating sections of ridges 25 and grooves 26, in a generally repetitive fashion. The ridges 25 and grooves 26 may have same width or different widths across the cross-section. The ridges and grooves may be symmetrical or non-symmetrical, having generally arcuate sections (which may be semicircular, elliptical, parabolic, parabolic, hyperbolic, U-shaped, etc.) as shown in FIG. 3B. The alternating ridges and grooves may be zigzag, in the form of symmetrical V-shaped (FIG. 3C), asymmetrical V-shaped (FIG. 3D), square or rectangular (FIG. 3E), and other symmetrical or non-symmetrical geometrical profiles. The corrugation may comprise a combination of the foregoing profiles across the same sheet. Different corrugated sheets may have a different corrugation profile.

While the wood grain directions in the corrugated sheets and non-corrugated sheets are illustrated herein as having a direction generally parallel or orthogonal to the longitudinal direction of the corrugation structure, the wood grains may be generally diagonal to the direction of the corrugation structure.

The corrugated sheet structure is formed by pressing with an appropriate press, using complementary pressing mold surfaces that are corrugated shaped. The pressing/molding process may include applying heat to the wood sheet to soften the wood. For example, relevant parameters for the formation of the corrugations may include moisture level (e.g., pre-molding moisture level of 20-25%; post-molding moisture level of 8-10%), pressure (e.g., 4-6 kg/cm²), and heat (e.g., 110-150° C.). The value of these parameters may be determined for the particular properties of the corrugated sheet, such as type and thickness of wood, corrugation structure, etc.

The corrugated wood sheet 24 may replace one or more of the flat wood sheets 12 in the stack 10. In another embodiment shown in FIG. 4, several corrugated wood sheets 24 may be stacked in a stack 28, with grains in an orthogonal relationship, or with the grains in the same direction. The stack 28 is applied to a press molding process similar to the process described above, to shape into a receptacle of a desired shape. Generally, a stack of corrugate wood sheets 24 is applied to shape articles having structural features involving more curvature and/or bending, and a stack of flat wood sheets is applied to shape articles having more planar surface features.

Using the stack 28 of corrugated wood sheets 24, the shaping of the receptacle may be facilitated during molding. The corrugation structure improves flexibility and moldability of the wood sheets, since the corrugation allows for easier expansion and contraction across the corrugated structure. Upon press molding of the stack 28 of corrugated wood sheets 24, it is easier for the corrugated sheet material to stretch and/or contract laterally in the planar direction (e.g., like an accordion), or “flow” by contracting or expanding the ridges and grooves sideways, to more easily conform to the shape of the molding blocks, with less tearing along the wood grains. Generally, for a stack of corrugated wood sheets having wood grains generally parallel in adjacent sheets, the stack is more flexible for bending about an axis in the direction of the grains, and more rigid about an axis orthogonal to the grains. Because of the multi-ply structure, adjacent layers provides reinforcement to reduce tearing, or even if there are tears along or across the wood grains, adjacent layers provide the necessary reinforcement to the torn areas. It is noted that upon pressing the stack 28 of corrugated wood sheets 24, the corrugations would be crushed to the extent that the corrugations may be difficult to be distinguished by viewing, but the layer of sheets nonetheless retain its natural wood grain, fiber structure and/or cellulose network in the pressed multi-ply panel or laminated structure.

FIG. 5 illustrates another embodiment of the stacking of a combination of flat and corrugate wood sheets, arranged with grains in parallel and orthogonal relationships. At A, the first sheet is a corrugated wood sheet 31. At B, another corrugated wood sheet 32 is stacked on top of the corrugated wood sheet 31 with grains aligned parallel between the sheets (i.e., the corrugation are align in parallel). At C, a flat wood sheet 33 is placed on top of the sheet 32. The grain direction of the sheet 33 is orthogonal to the grain direction of sheet 32. (Alternatively, the grain direction of the sheet 33 may be parallel to the grain direction of sheet 32). At D, a corrugated wood sheet 34 is placed on sheet 33, with the grain/corrugations orthogonal to that of sheet 32. At E, another corrugated wood sheet 35 is placed with grains orthogonal to that of sheet 34. Finally, a finishing sheet 36 is placed on top of sheet 35 and/or at the bottom of the sheet 31. The finishing sheet 36 may be a flat wood sheet (with grains either orthogonal or parallel to that of sheet 35 and/or sheet 31), or a lamination layer to enhance the finish of the multi-ply panel subsequently produced by pressing. The resultant stack 30 of layers of sheets 31 to 36 may be subject to pressing to pre-form a panel that can be used for constructing an article, and/or later to shape receptacles (see discussions below), or may be subject to press molding to shape into a receptacle in a single step as disclosed above. To facilitate retaining the relative positions of the various layers of the stack 30, glue may be applied between adjacent layers, before pressing to pre-form a panel.

In another embodiment of the present invention, the layering of thin wood layers may be strategically designed to provide different structural properties at different sections of the receptacle. The receptacle does not need to have uniform layers across the structure. Some sections may have more layers than other sections, and some sections may have orthogonal layers (e.g., at the edges of the receptacle, or at a section which serves as a handle for the receptacle where higher strength is desired) and other sections may have unidirectional layers, to provide the desired specific structural characteristics (e.g., rigidity, flexibility) at specific sections and the overall structural characteristics for the particular receptacle configuration. Different types of wood or other cellulose or non-cellulose, natural or synthetic materials may be provided in one or more layers, at one or more sections in the receptacle. The sheets may be arranged or distributed in a roof tile fashion, with cascading, staggering, terraced or feathered layers, such as to form a gradually thinning edge upon heat pressing.

FIGS. 6 to 8 illustrates several embodiments of different stacking of the wood sheets. In FIG. 6, two corrugated wood sheets 41 and 42 are stacked in a cascading or terraced fashion to resemble the tiling of roof, thereby to provide gradual feathering at the edge of the stack 40 (FIG. 6 only shows the edge section of the stack 60; the stack may extend to a larger area not shown in the figure). It is noted that the natural wood grain of the corrugated sheet 42 is generally in a direction across the ridges/grooves of the corrugation, as shown by the arrow, and orthogonal to the general direction of the wood grains in the corrugated sheet 41. More wood sheets may be provided, as in the stack 50 in FIG. 7. In FIG. 7, the stack 50 comprises corrugated wood sheets 51 and corrugated wood sheets 52, of similar corrugation direction but different grain directions. Further, a layer 53 is provided, which may be a flat wood layer, or a layer of another type of synthetic or natural material, like paper, metal foil, felt, plastic, mesh, gauze, perforated sheet, knitted or non-knitted fabric, glue, etc., which may or may not be biodegradable, environmentally friendly or food-grade. The layer 53 may be wood having grain direction generally in the same direction as sheets 51, but orthogonal to sheets 52 (alternatively parallel to sheets 52). As in the previous embodiment, the layers at the edge are “feathered” in a staggered, cascading or terraced fashion.

FIG. 8 shows an embodiment in which the stack 60 has at its edge section wood sheets stacked in cross grain fashion. (FIG. 8 only shows the edge section of the layers; the layers may extend to a larger area not shown in the figure.) Corrugated wood sheets 61 and 62 are of different grain directions with respect to the corrugations. By providing a cross grain arrangement, and further a cross-corrugation configuration, at the edge of the wood stack 60, the resultant compressed multi-ply panel (e.g., in the receptacle) would be reinforced to have higher strength properties. There is also an intermediate layer 63, which may be similar to layer 53 in FIG. 7, having wood grain generally parallel to the grain direction of either the top or bottom adjacent layer 62.

Further variation of the foregoing may be provided, by varying the number of layers of flat and/or corrugated wood sheets, thickness of the sheets, grain orientation, distribution of the layers and other physical properties across the plane of the stack, etc., to obtain specific structural and mechanical strength characteristics for different locations across the stack. For example, smaller pieces (i.e., pieces of smaller area not spanning across the layer below) of wood sheets may be positioned only near the edge of a panel structure, to added structural reinforcement to the panel at its edge. Such variations are well contemplated without departing from the scope and spirit of the present invention.

Alternatively, the flat and/or corrugated sheets are initially stacked and pressed to pre-form a generally planar panel having a combination of flat and/or corrugated sheets (see FIG. 5). Appropriate glue may be applied to the sheets of wood to fix the relative position of the sheets to form the generally planar panel structure. The panel is subsequently applied to a molding process to form the desired receptacle structure. The pressing of the stack (e.g., stack 30 in FIG. 5) to pre-form a panel requires significantly less pressure than the pressure required to shape a final article such as a receptacle shown in FIG. 2D. For example, the panel pre-forming pressure may be 0.2-0.4 kg/cm². In pre-forming the panel, the sheets may be pressed without fully compressing the ridges/grooves, so that air space is left between the ridges/grooves in a corrugated sheet and adjacent corrugated sheet and/or flat sheet. The resultant panel would still include visually discernable corrugations within the laminated structure.

More than one panel may be used to form the receptacle. Different panels having different corrugated structure and/or profiles, thicknesses of the layers of sheets, combination of layers, distribution of layers and/or structural characteristics and specification across the planar structure may be pre-formed. These panels are selectively applied to configure the base material structure for press forming the receptacle configuration. The panel structure is then subject to heat pressing to form the desired receptacle structure. To further facilitate shaping the panel structure into a receptacle, it may be subject to a softening step before the pressing step. The panel is placed in a preheated softening chamber, to soften the multilayer panel by heat and/or moisture. The pre-formed panels may be sized, shaped and assembled (e.g., by gluing) into an article, such as a receptacle.

The layers of sheets are stacked in the sequence as shown in the various figures, by way of examples and not limitations. However, it is contemplated that to the extent it is consistent with the features, functions and purpose of the present invention disclosed herein, the various layers may be stacked in a different sequence not shown. Intermediate layer or layers of materials of different or similar materials or structure (e.g., a buffer layer, a primer layer, a support layer, another wood or synthetic layer, corrugated or otherwise) may be present or provided between the layers mentioned and illustrated. The reference herein to one layer being coupled to, adjacent to, above, below, on, or under another layer does not necessarily mean immediately adjacent to, above, below, on, or under, and does not preclude the addition of intermediate layer or layers. Also, certain layer or layers disclosed herein may be omitted or replaced by other equivalent or different layer or layers of material. Furthermore, one or more of the layer structures may include a multilayered structure having sub-layers that are made of same or different materials. The layer structures shown need not be of a continuous structure. The layers need not be of uniform thickness throughout the layer. Other variations may be implemented without departing from the scope and spirit of the present invention.

In one embodiment, the wood used for processing and forming the wood multi-ply panel is selected from trees that are of the type that matures in relative short period of time, such as between 5 to 15 years. This type of trees is generally referred to as Green Wood, about 5-7 years old. For example, Poular trees may be harvested to produce the wood sheets. Poular trees (scientific name Poulus Spp) takes about 5 to 7 years to mature to a stage useful for the present invention. The tree limbs and bark are removed to produce a generally cylindrical tree trunk. The tree trunk may be cut to sections of the desired size. The sheets of wood are sliced generally along or with the grain of the wood. (It is noted that natural wood does not have perfect parallel grains. Accordingly, “with the grain”, “parallel to the grain”, and like terms as used herein refer to the general direction of the wood grain, as opposed to the lateral and/or perpendicular “against the grain”, “cross grain” or “orthogonal” directions, as is generally referenced in the wood industry.) In one embodiment, the sheets of wood are thinly sliced from a tree trunk in a circumferential spiral fashion, like the peeling of skin on an apple. A spiral-cutting machine may be used. It is noted that the sheets of wood thus obtained still retain their natural grain and/or long range cellulose structure with the sheets. The sheets do not comprise a meshed pulp structure as found in paper stock or wood pulp material.

The desired thickness of the sheets would depend on the type of trees and the application to form particular receptacles. Generally, for Poular wood, the local thickness t (see FIG. 3B) of the corrugated sheets may vary from about 0.01 to 0.3 mm, preferably 0.1 to 0.3 mm, the width w (see FIG. 3B) of the grooves and ridges may range between 2-3 mm, and the overall thickness T (see FIG. 3B) of the corrugated sheet structure may range between 2-3 mm.

The pressure and temperature of the molding process would depend in part on the particular type of wood material and the shape of the receptacle configuration. By way of example and not limitation, for Poular wood, the molding process for a generally rectangular body, like a tray of about 25 cm×20 cm area, is carried out at a pressure of about 5 to 8 kg/cm², at a temperature of about 130 to 150° C., for a stack of 3 to 6 sheets of corrugated wood sheets. The moisture content of the wood sheets should be about 20 to 25 percent by weight. The heated moisture softens the wood sheets as they are pressed by the mold. During the molding process, the pressure on the stack of wood reduces the overall thickness to a final thickness that is about 15 to 20% of its original uncompressed thickness (in the case the wood sheets 12 were not preformed to a panel prior to molding), or about 10 to 15% of the original thickness of the preformed panel of wood sheets (i.e., further compressing the preformed panel).

FIGS. 9A to 9D illustrates a receptacle in the form of a container 70 in accordance with another embodiment of the present invention. The container 70 is generally cylindrical, having a square cross section as shown in FIG. 9B. It comprises a generally body section 72 having a flap 71, and end caps 73 and 74, defining an opening 75. When the flap 71 closes onto the body section 72 (indicated by arrow in FIG. 9B), it covers the opening 75 of the container 70. The entire construction of the container 70 may be made from wood panels in accordance with the present invention described above. For example, the end caps 73 and 74 may be molded from corrugated wood panels comprising at least one corrugated sheet and a finishing wood layer to obtain the profile shown in FIGS. 9C and 9D. The wood grains in the layers for the end caps 73 and 74 may be orthogonal to provide strength and rigidity. The body section 72 including the flap 71 may be made of at least one corrugated wood panel with appropriate finishing wood layer, wherein the wood grains may be parallel (with perhaps one layer that is orthogonal in grain direction) to provide more flexibility for bending about the axis of the body section. Spacer 76 and 77 may be provided at the joints of the end cap to the body section 72. FIG. 9D illustrates the view with the flap 71 closed onto the stop 71, so as to cover the opening 75 in the container 70. The overall structure of the container is relatively strong in the axial direction, with flexibility in the circumferential direction, and sufficient desired strength in the axial direction. The container 70 may be useful as a gift wrap to hold a wine bottle, or a container to hold a scroll of paper or drawing.

As can be appreciated, there is infinite number of ways the wood panels in accordance with the present invention may be used to construct various articles of various shapes and sizes. The inventive wood panel can be used as a substitute for wood sheets, paper sheets, plastic sheets and even metal sheets. The inventive wood panel is primarily made of natural wood material that retained its natural fiber, grain and/or cellulose composition and/or structure; such structure is recognizable or distinctive even after pressing and molding treatments.

The present invention as described in detail above provides at least the following advantages over the prior art plastic, paper or wood receptacles:

The present invention makes use of wood from trees that matured in a relatively short period of time, thereby conforming to the resources approved by United Nations, which would meet worldwide acceptance. The manufacturing, use and disposal of the receptacles meet environmental protection objectives, with reduced pollution, less waste in raw materials, less byproducts, and any waste produced is largely biodegradable. The receptacles retain the natural cellulose and grain structure of natural wood, which allow for simple fabrication, reducing production costs. Given less waste in raw material by spiral cutting to form wood sheets, the utility of the raw material is improved, significantly saving wasted natural resources. The multiple layered corrugated structure inherently result in a structure having improved mechanical strength. Further, by arranging the relative grain directions in the multi-ply panel, the resultant structure is stronger against tearing or cracking, even for a thin multi-ply panel structure. A corrugated panel may be formed with different sections of different materials and/or structure, to obtain different structural characteristics at the different sections. The receptacle molding process at high heat kills pests and disinfects the receptacle, thus improving the hygiene and safety of the receptacle, and easily meeting health, animal and/or agricultural control requirements worldwide. The multi-ply panel may be applied to mass-produce receptacles such as plates, boxes, utensils, bags, etc., for the food industry.

While the invention has been described with respect to the described embodiments in accordance therewith, it will be apparent to those skilled in the art that various modifications and improvements may be made without departing from the scope and spirit of the invention. For example, the layers of a multi-ply panel may be made of layers of different types of wood, or different types of cellulose or non-cellulose, natural or synthetic materials, without departing from the scope and spirit of the present invention. The panel may be made entirely out of wood, or a combination of wood and other non-wood materials. While food containers and receptacles were described by way of examples, the multi-ply panel structure of the present invention may be applied to make other types of containers and receptacles, such as boxes, bags, packaging, etc. for perishable or non-perishable, food or non-food items. Further the multi-ply panel structure may be applied to other than receptacles, for example as panels for constructing items such as book covers, wrapping sheets, and other applications in which the multi-ply panel structure may replace thin plastic, wood pulp and/or paper structures.

Accordingly, it is to be understood that the invention is not to be limited by the specific illustrated embodiments, but only by the scope of the appended claims. 

1. A wood panel, comprising at least a first ply of wood having an initial corrugated structure prior to forming the wood panel.
 2. The wood panel as in claim 1, wherein the first ply of wood in the corrugated structure retains at least one of its wood grains, fiber structure, or cellulose structure after forming the wood panel.
 3. The wood panel as in claim 1, wherein the first ply of wood has wood grains generally in a direction parallel, orthogonal or diagonal to a longitudinal direction of the corrugated structure.
 4. The wood panel as in claim 1, wherein the corrugated structure has a sectional profile comprising alternating symmetrical or asymmetrical sections.
 5. The wood panel as in claim 4, wherein each of the section resembles at least one of the following:V-shape, U-shape, arcuate, semi-circular, rectangular, sinusoidal, hyperbolic, parabolic, or elliptical.
 6. The wood panel as in claim 1, comprises at least a second ply of material having a generally flat structure, wherein the second ply of material is coupled to the first ply.
 7. The wood panel as in claim 6, wherein the second ply comprises at least one of a synthetic or non-synthetic material.
 8. The wood panel as in claim 7, wherein the synthetic or non-synthetic material comprises at least one of: knitted fabric, non-knitted fabric, felt sheet, metal sheet, wood sheet, paper sheet, plastic sheet, glue sheet, mesh sheet, perforated sheet or gauze sheet.
 9. The wood panel as in claim 6, wherein the second ply comprises a wood sheet, wherein the first ply and the second ply have grain directions that are generally in same direction, orthogonal or diagonal to each other.
 10. The wood panel as in claim 6, wherein the second ply initially has an initial corrugated structure prior to forming the wood panel.
 11. The wood panel as in claim 6, wherein the second ply does not extend to cover the entire first ply, wherein the second ply is located at one or more sections with respect to the first ply to provide reinforcement of the wood panel at said one or more sections.
 12. The wood panel as in claim 6, wherein the second ply and the first play define a space between the corrugated structure of the first ply and the second ply.
 13. An article of manufacture, comprising a body including the wood panel as in claim
 1. 14. The article of manufacture as in claim 13, wherein the body comprises a receptacle having a laminated wall structure of which the wood panel is a part.
 15. A receptacle for packing or serving food, comprising a body section for holding food, having a laminated wall structure that comprises primarily wood.
 16. The receptacle as in claim 15, wherein the laminated wall structure comprises at least one layer of wood having an initial corrugated structure prior to forming the laminated wall structure.
 17. A process for forming a wood panel structure, comprising: providing a first ply of wood having a corrugated structure; providing a second ply of material; and coupling the first ply to the second ply.
 18. The process of claim 17, wherein the step of coupling comprises at least one of gluing or pressing the first ply to the second ply, without or without an intermediate layer.
 19. The process of claim 18, further comprises pressing the first and second ply to form an article have a wall section of which the wood panel structure is a part.
 20. An article of manufacture, made in accordance with the process of claim
 17. 